Spanish or French would be best in terms of effort needed/possible use you get out of them, I think. If you speak English, Spanish and French, you are pretty much set for a very large part of the world.
In your case, though, German might be best, to beg more efficiently for Euros ("Gib mir Geld, du Schweinehund, ich verrecke sonst hier!"). Although French could also help, since EU is mostly a German-French alliance with some bandwagoners.